Implantable medical devices (IMDs) include devices designed to be implanted into a patient. Some examples of these devices include cardiac function management (CFM) devices such as implantable pacemakers, implantable cardioverter defibrillators (ICDs), cardiac resynchronization therapy devices (CRTs), and devices that include a combination of such capabilities. The devices can be used to treat patients using electrical or other therapy, or to aid a physician or caregiver in patient diagnosis through internal monitoring of a patient's condition. The devices may include one or more electrodes in communication with one or more sense amplifiers to monitor electrical heart activity within a patient, and often include one or more sensors to monitor one or more other internal patient parameters. Other examples of implantable medical devices include implantable diagnostic devices, implantable drug delivery systems, or implantable devices with neural stimulation capability.
IMDs typically have an electronics unit that includes one or more integrated circuits (ICs) designed to perform a variety of functions, such as timing or to provide therapy. The minimum size of transistors in the ICs continues to be reduced as technology advances. This miniaturization trend continues to allow more and more transistors to be placed on a die. This additional circuitry has in turn provided an increase in circuit performance, and allowed an increased number of device features and therapies to be included in the IMDs. In the past, as transistor device feature sizes decreased, the main concern of IMD design was to put more functionality in an IC and less concern was given to altering design techniques to accommodate the reduced feature size.